@@ -4,7 +4,7 @@ use rustc_abi::{BackendRepr, TagEncoding, Variants, WrappingRange};
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use rustc_hir:: { Expr , ExprKind , HirId , LangItem } ;
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use rustc_middle:: bug;
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use rustc_middle:: ty:: layout:: { LayoutOf , SizeSkeleton } ;
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- use rustc_middle:: ty:: { self , Ty , TyCtxt , TypeVisitableExt } ;
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+ use rustc_middle:: ty:: { self , AdtKind , Ty , TyCtxt , TypeVisitableExt } ;
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use rustc_session:: { declare_lint, declare_lint_pass, impl_lint_pass} ;
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use rustc_span:: { Span , Symbol , sym} ;
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use tracing:: debug;
@@ -935,6 +935,38 @@ fn get_nullable_type_from_pat<'tcx>(
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}
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}
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+ /// determines wether or not `outer_ty` is an option-like enum, with the same size as its contained type, `ty`.
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+ /// this ASSUMES that `ty` is a type that is already 'inside' of `outer_ty`.
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+ fn is_outer_optionlike_around_ty < ' tcx > (
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+ cx : & LateContext < ' tcx > ,
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+ outer_ty : Ty < ' tcx > ,
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+ ty : Ty < ' tcx > ,
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+ ) -> bool {
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+ // three things to check to be sure outer_ty is option-like (since we know we reached the current ty from there)
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+ // That outer_ty is an enum, that this enum doesn't have a defined discriminant representation,
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+ // and the the outer_ty's size is that of ty.
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+ if let ty:: Adt ( def, _) = outer_ty. kind ( ) {
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+ if !matches ! ( def. adt_kind( ) , AdtKind :: Enum )
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+ || def. repr ( ) . c ( )
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+ || def. repr ( ) . transparent ( )
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+ || def. repr ( ) . int . is_none ( )
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+ {
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+ false
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+ } else {
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+ let ( tcx, typing_env) = ( cx. tcx , cx. typing_env ( ) ) ;
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+
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+ // see the insides of super::repr_nullable_ptr()
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+ let compute_size_skeleton = |t| SizeSkeleton :: compute ( t, tcx, typing_env) . ok ( ) ;
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+ match ( compute_size_skeleton ( ty) , compute_size_skeleton ( outer_ty) ) {
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+ ( Some ( sk1) , Some ( sk2) ) => sk1. same_size ( sk2) ,
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+ _ => false ,
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+ }
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+ }
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+ } else {
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+ false
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+ }
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+ }
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+
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declare_lint_pass ! ( VariantSizeDifferences => [ VARIANT_SIZE_DIFFERENCES ] ) ;
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impl < ' tcx > LateLintPass < ' tcx > for VariantSizeDifferences {
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